1. Field of the Invention
The present invention relates to an electronic apparatus, especially to an electronic apparatus including a plurality of external connection connectors.
2. Description of the Related Art
While electronic apparatuses are desired to have higher performances and more functions, external interfaces connecting an electronic apparatus to an external apparatus diversify, so that electronic apparatuses are required to be compatible with many types of external interface specifications. At the same time, as electronic apparatuses evolve, specifications of external interfaces become more speedy and more functional, so that electronic apparatuses are required to be compatible with interfaces of many signal pins and a differential signaling method.
Therefore, not only a plurality of external interface connectors need to be mounted on an electronic apparatus, but also connecters with many pins need to be mounted to transmit/receive many signals on a per-connector basis, so that a necessary space to mount these connecters increases.
To transmit external connection signals by the differential signaling method, an impedance control of internal wiring pattern is required according to the differential signaling specification. Therefore, the wiring pattern of a differential signal from a driver IC to an external connection connector needs to be formed so that a desired differential impedance is obtained.
Therefore, conventionally, as a configuration which can easily eliminate causes of impedance disruption such as a wiring connection between boards via connectors, and easily control the impedance, the driver IC and external connection terminals are arranged on the same board. However, as downsizing and thinning of electronic apparatuses progress, when all the external connection connectors are arranged on a main board, an area and thickness of the main board need to increase, so that the main board becomes an obstacle to downsizing a camera.
As an electronic apparatus which can connect to a plurality of external interfaces, Japanese Patent Application Laid-Open No. 2007-166290 discusses an electronic apparatus in which a separate board on which a plurality of external connection connectors are mounted is connected to the main board by using a flexible printed circuit board.
However, in the conventional arrangement configuration of the external connection connectors, since the external connection connectors are aligned and arranged on the separate board, a space to align the connecters is needed, so that there is a problem that the conventional arrangement configuration is not suited for downsizing of the apparatus.
Further, although a connecting wiring from the external connection connector to the main board needs a width large enough for a plurality of interface signals, the space for the wiring cannot be obtained when the apparatus is downsized. When there is no space for the wiring, the wiring for the connection is formed by a multilayer board or a plurality of connection boards; however, the multilayer board is expensive. On the other hand, when the external connection connector includes a plurality of differential signals, wiring which controls impedance is generally formed on the surface layer. Therefore, when the width of the board is not large enough for the wiring, the wiring is formed on both surfaces of the board.
However, when the pattern is connected from the surface on which the connector is mounted, to the reverse surface of the board, the pattern is connected through a through-hole, so that the impedance is disrupted. Further, when connecting the pattern by piling up a plurality of connection boards, there is a problem that the impedance-controlled wiring pattern is affected by a wiring pattern of another connection board, and the impedance is disrupted.